Method for servicing a duplexer having a radio frequency assembly

Abstract

A method for servicing a duplexer having a cavity resonator defining an opening covered by an RF plate. The RF plate defines an opening through which a pass-band tuning pipe extends and is secured thereto. A collar is attached to one end of the pipe, and at least one steel set screw extends into the interior of the collar, the at least one end having a soft (e.g., brass) tip. A tuning plunger is slidingly positioned within the pass-band tuning pipe. A rod is attached to a first end of the tuning plunger and extends through the collar, the rod being fabricated from a material harder than the tip of the at least one set screw. The at least one set screw is configured for tightening down on the rod to secure the rod and tuning plunger in place. A trimmer capacitor is positioned in the RF plate.

The invention claimed is: 
     
       1. A method for servicing a duplexer having a radio frequency (RF) assembly configured for fitting over an opening defined in a cavity resonator of the duplexer, wherein the RF assembly comprises:
 an RF plate; 
 first and second RF connectors secured to the RF plate and configured for receiving respective first and second co-axial cables carrying RF signals; 
 an RF junction bar connecting the first and second RF connectors; 
 a trimmer capacitor positioned in the RF plate; 
 a coupling loop coupling the RF junction bar to the trimmer capacitor positioned in the RF plate; 
 a hole defined in the RF plate; 
 a pass-band tuning pipe extending through the hole and secured to the RF plate, the pipe having a first end and a second end; 
 a shaft-locking collar attached to the first end of the pipe, the collar defining an interior portion and at least one threaded hole for receiving at least one set screw having at least one end extending into the interior portion of the collar; 
 a tuning plunger having a rod attached to one end of the tuning plunger, the plunger extending slidingly through the tuning pipe and collar, wherein a tip of the at least one set screw is fabricated from a material softer than the rod, the at least one set screw being configured for tightening on the rod to secure the rod and tuning plunger in place; and 
 one or more fasteners for securing the RF plate over the opening of the cavity resonator; and; 
 wherein the method comprises steps of: 
 adjusting the tuning plunger by raising and lowering it until the insertion loss at the pass-band is minimized, and the return loss at the pass-band is maximized; 
 securing the tuning plunger in place using set screws on the collar, which set screws engage the rod on the tuning plunger; and 
 adjusting the trimmer capacitor until the insertion loss at the reject-band is maximized, and the return loss at the reject-band is minimized. 
 
     
     
       2. The method of  claim 1  wherein the method further comprises the step of:
 connecting via coax cables the duplexer to a spectrum analyzer/tracking generator; and the steps of adjusting further comprise: 
 adjusting the tuning plunger by raising and lowering it until the insertion loss at the pass-band as determined by the spectrum analyzer/tracking generator is minimized, and the return loss at the pass-band as determined by the spectrum analyzer/tracking generator is maximized; and 
 adjusting the trimmer capacitor until the insertion loss at the reject-band as determined by the spectrum analyzer/tracking generator is maximized, and the return loss at the reject-band as determined by the spectrum analyzer/tracking generator is minimized. 
 
     
     
       3. The method of  claim 1  wherein the method further comprises the step of:
 connecting via coax cables the duplexer to a vector network analyzer; and the steps of adjusting further comprise: 
 adjusting the tuning plunger by raising and lowering it until the insertion loss at the pass-band as determined by the vector network analyzer is minimized, and the return loss at the pass-band as determined by the vector network analyzer is maximized; and 
 adjusting the trimmer capacitor until the insertion loss at the reject-band as determined by the vector network analyzer is maximized, and the return loss at the reject-band as determined by the vector network analyzer is minimized. 
 
     
     
       4. The method of  claim 1  further comprising positioning a gasket between the RF plate and the duplexer. 
     
     
       5. The method of  claim 1  further comprising positioning a gasket between the RF plate and the duplexer, wherein the gasket comprises a conductive elastomer. 
     
     
       6. The method of  claim 1  wherein surfaces of the RF assembly in the interior of the cavity resonator are silver plated. 
     
     
       7. The method of  claim 1  wherein the cavity resonator is manufactured from copper. 
     
     
       8. The method of  claim 1  wherein the rod is manufactured from invar. 
     
     
       9. The method of  claim 1  wherein the tip of the at least one set screw is fabricated from brass. 
     
     
       10. The method of  claim 1  wherein the trimmer capacitor is a ceramic air variable capacitor. 
     
     
       11. The method of  claim 1  wherein the trimmer capacitor is an air trimmer capacitor. 
     
     
       12. The method of  claim 1  wherein the trimmer capacitor is a ceramic trimmer capacitor. 
     
     
       13. The method of  claim 1  wherein the first and second RF connectors are one of N-type connectors, BNC connectors, TNC connectors, and 4.3/10 connectors.